关键响应者没有响应

Question

我正在尝试实现一项功能，其中当我按空格键时会切换计时器。不幸的是，空格键没有反应，我不确定自己做错了什么。任何帮助都非常感谢！

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import java.awt.*;
import java.awt.event.*;
import java.util.Random;
import javax.swing.*;


public class Life extends JPanel implements ActionListener {

    public static final int SIZE = 15; // map dimension
    public static final int CELL_SIZE = 25; //size of cells
    public static final int UPDATE = 1000; //rate of updating

    public char[][] map; // current values of map
    public char[][]temp_map; // store changes while calculating


    //constructor
    public Life() {
        map = new char[SIZE][SIZE];
        temp_map = new char[SIZE][SIZE];

        //to hear key events
        KeyResponder key = new KeyResponder();
        addKeyListener(new KeyResponder());
        setFocusable(true);



    }

    // Inner class for responding to key events
    private class KeyResponder extends KeyAdapter {

        // Method that runs whenever a key is pressed
        public void keyPressed(KeyEvent e) {
            switch (e.getKeyCode()) {
                case KeyEvent.VK_SPACE:
                    System.out.println("test");
                    pause();
                    break;


            }
        }
    }